New tools to aid Michigan apple and tart cherry exporters

New tools guide Michigan apple and tart cherry growers in selecting insecticides to manage key pests close to harvest so as not to exceed target market MRLs.

Members of the Michigan State University Extension fruit team have developed a set of new tools in support of Michigan apple and tart cherry exporters, funded in part by the Michigan Apple Committee, the Michigan Cherry Committee and the MDARD Strategic Growth Initiative (USDA Technical Assistance for Specialty Crops Program Agreement No. 2013-30). Given that a number of important export markets have pesticide residue tolerances that are lower than those set by the U.S. EPA, six insecticides registered for use on apples and five insecticides registered for use on tart cherries were tested to evaluate their rate of degradation after application. Degradation curves were used to develop a set of adjusted pre-harvest intervals (PHIs) that would comply with the maximum residue limits (MRLs) of U.S. and selected export markets.

The tools are meant to provide guidance to Michigan apple and tart cherry growers in selecting materials to manage key pests close to harvest with a particular market in mind. Selected markets have been included, provided by Michigan Apple Committee and the Cherry Marketing Institute, some of which have more restricted MRLs than required by the United States for particular materials. The MRLs used to develop this tool come from those published by Bryant Christie, Inc. as of May 2015. The data used to determine whether a longer PHI would be necessary for a given market and its published MRL are based on a single application made near the legal PHI for each material tested, in replicated trials conducted at Michigan State University orchards and laboratories. Residue analysis followed a generally accepted standard protocol known as the QuECHERS method on freshly harvested apples and rinsed tart cherries.

Each tool is in the form of colored charts to indicate when the insecticides tested would or would not be safe to use given a target market. Red used in the chart means the product should not be used during this time either because of EPA label restrictions or due to a high risk of exceeding MRLs for a given market. Yellow used in the chart means the product should be used with caution during this time given all the variables (e.g., tank mixes, application method and calibration, use of adjuvants, environmental conditions post-application and post-harvest handling) that can impact the time it takes for a residue to degrade in order to meet the MRL for a given market. Green used in the chart means that the product is likely to be safe for use at this time with low risk of residue remaining at harvest that would exceed MRLs for a given market.

Download a PDF version of the apple charts or tart cherry charts, or contact me at jkwilson@msu.edu to receive a free laminated copy. For more information about the project in general, please contact Mark Whalon at whalon@cns.msu.edu. Mark Whalon of MSU Department of Entomology led this collaborative project with John Wise, Larry Gut, Nikki Rothwell and Julianna Wilson.

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